1. Field of the Invention
The present invention is directed to a novel synthetic process for preparing esters of catechol amines and other sympathomimetic amines in optically active or racemic form, and to novel N-tert-butoxycarbonyl intermediates useful in the subject process.
2. Description of the Prior Art
U.S. Pat. Nos. 3,809,714, 3,825,583, 3,839,584, 3,868,461, 3,959,485, 3,966,749, 3,908,017, 4,035,405, 4,088,783, 4,145,441 and 4,158,005, all in the name of the instant assignee, disclose a number of sympathomimetic amine derivatives within the general formula (I) set forth hereinbelow, and nontoxic pharmaceutically acceptable acid addition salts thereof. The compounds of formula (I) and their salts are useful in the treatment of conditions responsive to sympathomimetic amines, e.g., glaucoma, asthma and nasal congestion.
Prior art methods for the preparation of compounds within the scope of the formula (I) below generally have provided the compound in the form of a racemic mixture, i.e., a mixture containing both the biologically active and the biologically inactive isomer. Normally, the compounds of formula (I) have been administered in the form of a racemic mixture, as the means to separate the optically active, biologically active isomers from their racemic mixtures are tedious and expensive. In fact, resolution of the racemic mixtures of many of the compounds of formula (I) has not been reported in the literature.
Consequently, it is apparent that a need exists for a means of directly synthesizing the optically active, biologically active forms of the compounds of formula (I), thus avoiding the necessity of first obtaining the racemic mixture and then either resolving the racemic mixture and administering the optically and biologically active isomer thereof, or else, as is more frequently the case, administering the racemic mixture itself. In the latter case, it is apparent that the dosage amount of a racemic mixture which would be required to achieve therapeusis would be much greater than that required if only the optically active, biologically active isomer were administered.